Solar environments such as the solar atmosphere, interplanetary medium, and planetary magnetospheres evolve in time and space through the dynamic transfer of mass, momentum, and energy between the embedded electromagnetic fields and the constituent plasma and energetic particle populations. Thus, a complete characterization of plasma and particle environments covering the energy range of from a few eV up to tens of MeV is critical for many current and future Planetary and Heliophysics missions.
Presently, two or more instruments based on distinct measurement techniques are used to cover the large range in energies from thermal (˜eV) to energetic (10 s of MeV) particles. Energetic particle instruments covering the energy range from tens of keV up to a few MeV use either solid state detectors (SSDs) to measure the residual energy (E′) of the incoming particles, e.g., Cassini/Low-Energy Magnetospheric Measurement Systems-LEMMS, S. M. Krimigis et al, “Magnetosphere Imagining Instrument (MIMI) on the Cassini Mission to Saturn/Titan”, Space Sci. Rev. 114, 233-329 (2004), or the Time-Of-Flight (TOF, τ) vs. Residual Energy (E′) measurements in SSDs, e.g., PEPSSI on New Horizons, J. R. L. McNutt et al, “The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on the New Horizons Mission”, Space Sci. Rev. 140, 3150385 (2007). Occasionally, instruments such as the Charge-Energy-Mass-Spectrophotometer (CHEMS) on Cassini use electrostatic analyzers (ESAs) to perform energy-per-charge (E/q) analysis followed by TOF vs. E′ of suprathermal ions. In contrast, plasma populations from a few eV to up to tens of keV are typically measured using simple ESAs that select ions in a narrow E/q range (e.g., New Horizons/Solar Wind Around Pluto-D. McComas et al, Space Sci Rev. 140, 261-313 (2008) then focus them onto electron multiplier detectors such as microchannel plates (MCPs) or channel electron multipliers (CEMs) or use an ESA followed by TOF measurements that provide the speed of the incoming particles (e.g. D. J. McComas et al, “The Jovian Auroral Distributions Experiment (JADE) on the Juno Mission to Jupiter” Space Sci. Rev. (published online).
The allocation of resources required by two or three separate instruments for obtaining complete information about energy, arrival direction, ionic charge state, and mass of individual ions often involves trade-offs and compromises that typically result in significant gaps in the energy coverage or even a complete lack of information about the ion's ionic charge state or mass. As a result, many key properties of ion populations and dynamics in a wide variety of space environments such as the interplanetary medium, the Earth's magnetosphere, and the magnetospheres of the outer planets are not fully explored.